Power semiconductor modules comprise one or more power semiconductor chips. To dissipate the heat materializing in operation of the module the power semiconductor module is usually bonded to a heatsink. This mostly involves employing a complicated system of multiple bonds so that the pressure is evenly distributed.
In addition, the module is often electrically and mechanically bonded to a user-specific gating circuit, this again necessitating a complicated system of multiple bonds for the necessary electrical connections.
The power semiconductor chips of the module are usually mounted on one or more ceramic substrates because of their coefficient of thermal expansion, for one thing, being hardly different to the coefficient of thermal expansion of the semiconductor chips used, and, for another, because they achieve good dissipation of the heat materializing from operation of the power semiconductor chips.
One known possibility of incorporating one or more ceramic substrates componented with power semiconductor chips in a power semiconductor module is to mount all ceramic substrates used on a common solid metal baseplate, the underside of which simultaneously forms the underside of the module and to apply the power semiconductor module by its underside to a heatsink. But, the baseplate hampers good thermal contact between the substrates and the heatsink.
An alternative configuration eliminates the need of a solid metal baseplate. To attain an even distribution of the contact pressure between the substrates and the heatsink the individual substrates are pressed either along their circumferential side edges by the module housing to the heatsink which is bonded to the heatsink by a system of multiple bonds, or each of the substrates features fastener holes so that, for example by means of a screw, a contact pressure can be generated in the interior portion of the substrate in the direction of the heatsink. However, such power semiconductor modules having no common baseplate have either the disadvantage of a complicated system of multiple bonds between the power semiconductor module and the heatsink or mounting holes need to be fabricated in the ceramic substrates, again adding to the complications, taking up valuable space on the substrate, detrimenting dissipating the heat to the heatsink and, to make matters worse, risking a ceramic fracture in the region of each hole.
Furthermore, the more the number of power semiconductor chips incorporated in a power semiconductor module the larger the substrates needed, the greater the footprint thereof, making it all the more difficult to attain a uniform contact pressure of the substrates against the heatsink. In addition to this an expansive substrate componented with a plurality of power semiconductor chips has to be singled out from use or repaired, which is complicated, when even just one of the power semiconductor chips develops a fault.
There is a need for a power semiconductor module comprising no common metal baseplate mounting the substrates of the module and which can be simply mounted on a heatsink with a few bonds whilst in addition permitting bonding to a user-specific gating circuit.